Conventional surface acoustic wave device (hereinafter referred to as a device) having a plurality of pass band frequencies have been provided by forming several surface acoustic wave elements (hereinafter referred to as elements) corresponding to respective pass band frequencies on an individual piezoelectric substrate, then disposing the individual element in a package, and mounting a plurality of packages on a separate circuit board to connect the packages electrically.
In the above-configured device where the elements are packaged individually, interaction among the elements can be reduced. However, the device downsizing is difficult because of the plurality of packages.
Japanese Patent Laid-Open Publication No. H5-167389 discloses a method to solve the above problem. According to the method, a plurality of elements are housed in a package, and integrated. Thereby, the number of packages can be reduced and the device size can be made smaller. Another known method is to provide a plurality of elements 2 and 3 formed on a single piezoelectric substrate 1, as shown in FIG. 9. Output terminal electrode 4 and input terminal electrode 5 of the elements 2 and 3 are directly connected using connection electrode 6, and the elements are housed in a single package.
However, when a plurality of elements is housed in a single package, a certain specific space within the package for the elements is necessary. This limits further downsizing of a device. Moreover, when a plurality of elements is provided on a single piezoelectric substrate and electrically connected directly together, the plurality of elements affect each other to deteriorate attenuation characteristics.